The town's name probably derives from the name of the river, where the village stands, known as Rio San Lorenzo, which has its source by Mount Folly, and, before reaching the sea, it receives the waters of several streams. It is one of the smallest towns in the province of Imperia, but at the same time, it is one of most densely populated parts of the Riviera di Ponente. The local ecomony is based on tourism, floriculture and the production of Vermentino wine.
The village is divided into two parts: one stretching along the coast, the other on the hilly side, towards the Church entitled to Santa Maria Maddalena. The town, seen from above, resembles the shape of a large anchor. Numerous artificial reefs, created to protect the coast by sea currents, create a small marina, which is useful in Summer as a shelter for the boats.
In the XII century the Lengueglia ceded the fief of Pietrabruna to Porto Maurizio. The lords of Porto Maurizio built a new settlement on the left bank of the river San Lorenzo, just in front of the village already located on the right bank, that still belonged to the Lengueglia. The two communities coexisted peacefully for a long time. The inhabitants of the new settlement used the mouth of the river to allow the landing of ships and fishing boats. In 1284 the sailors of the village of San Lorenzo allied to the Republic of Genoa and actively took part to the famous battle of Meloria against the fleet of Pisa. In 1749 the two villages were united in one religious community and after the conquest by Napoleon in the late XVIII century, the town proclaimed its official administrative annexation. In 1831 a bridge in brick was built over the river and this made the connections between the two districts easier. At present the town has, however, two souls: one predominantly maritime and the other rural.

Not to miss
The Parish Church entitled to St. Mary Magdalene that, according to the legend, sheltered here during her escape towards Marseilles, due to the persecution of Christians in the Holy Land. Built close to the sea, the foundations are dated to the period between the XIII and XIV centuries. The structure was remodeled in 1766 in Baroque style, as evidenced by a cobbled inscription, placed in the courtyard and shaded by trees. The adjacent Bell tower, whose plaster affected by constant attacks of salt, over the years has had to receive numerous restorations. Within the church preserves a series of frescoes by anonymous authors and a wooden choir, that consists of eleven panels.